1. Field of the Invention
This invention generally relates to toothbrushes and, more particularly, to convertible toothbrushes whose bristles can be changed to a convex, concave or straight bristle configuration at the will of a user.
2. Description of the Related Art
It is known that, for proper cleaning of the exterior surfaces of teeth, toothbrush bristles should advantageously be shaped in a concave configuration. On the other hand, inner surfaces of the teeth are best cleaned when the bristles are shaped in a convex configuration. Conventional toothbrushes having bristles of a fixed contour have been made with either a convex or a concave bristle configuration, but not both. Hence, such single-configuration toothbrushes cannot properly clean both the interior and exterior tooth surfaces with the same degree of cleaning efficiency.
It has heretofore been proposed, for example, in U.S. Pat. No. 3,935,611, to provide a body brush having multiple bristle sections, one bristle section being convex while another bristle section is concave, but such large-sized body brushes are difficult to manipulate and, in any event, are not designed to readily fit inside a user's mouth. Convertible toothbrushes such as disclosed in U.S. Pat. No. 1,968,411, which are designed to readily fit in one's mouth, still are awkward to manipulate because at least one of the bristle sections must be moved relative to the other to obtain the desired bristle configuration.
Conventional toothbrushes, in which a single bristle section contour is changeable, have been proposed in U.S. Pat. Nos. 2,429,437; 2,864,111; 4,409,701 and 2,254,365. However, such convertible toothbrushes all require the use of at least one rotary or slidable actuator incorporated into the toothbrush, thereby necessitating a multi-partite, complex and costly product. The known convertible toothbrushes have proven to be generally unreliable and awkward in use.